NCERT Class 7 Mathematics

RATIONAL NUMBERS 185

Similarly,

75

88

+ would be

What do you get?

Also,
75 75?
88 8

• 
  
  
  
  • Are the two values same?
  
  
  
  

So, we find thatwhile adding rational numbers with same denominators, we add
the numerators keeping the denominators same.

Thus,

11 7 11 7 4

55 5 5

+ +

How do we add rational numbers with different denominators? As in the case of
fractions, we first find the LCM of the two denominators. Then, we find the equivalent
rational numbers of the given rational numbers with this LCM as the denominator.
Then, add the two rational numbers.

For example, let us add^72 and
53

.

LCM of 5 and 3 is 15.

So,

721 210and

515 315

Thus,
721 ()^210 ()
5 3 15 15

+ +

31

15

Additive Inverse

What will be

(^44)?
77

• 44 44 0
  77 7


• 
  
  
  
  • 
    
  
  
  
  

. Also,

(^440)
77
+⎛⎞
⎜⎟⎝⎠.
TRY THESE
Find:^136
77

• ,
  19 7
  55


• 
  

  TRY THESE
  Find:
  (i)
  32
  73

  
  


• 
  

  (ii)
  53
  611

  
  


• 
  

  7
  8
  6
  8
  5
  8
  4
  8
  3
  8
  2
  8
  1
  8
  0
  8
  1
  8
  2
  8
  3
  8
  5
  8
  4
  8